When a dye image is formed using a silver halide light-sensitive color photographic material, an aromatic primary amine color developing agent is oxidated when it reduces silver halide in an exposed light-sensitive silver halide color photographic material, thereby the resultant oxidation product reacts with a coupler preliminarily contained in the light-sensitive silver halide color photographic material so as to form a dye. Usually, in such an image forming system, a color reproduction technique based on the subtractive color process is used, wherein the light-sensitive silver halide color photographic material used comprises the blue-sensitive, green-sensitive, and red-sensitive silver halide emulsion layers correspondingly have yellow-dye forming, magenta-dye forming, and cyan-dye forming couplers, i.e. couplers whose sensitivities complementary to the color sensitivities of these emulsion layers.
The couplers useful for forming the yellow dye image include acylacetanilide couplers; and the couplers useful for forming the magenta dye image include pyrazolone, pyrazolobenzimidazole, pyrazolotriazole, and indazolone couplers; while the examples of the commonly used cyan dye image forming couplers include phenol and naphthol couplers.
The so-obtained image is required to be stable even when exposed to light for a long time, or even when stored under a high temperature or high humidity. Especially, a silver halide color photographic light-sensitive material (hereinafter referred to as color photographic material) which does not cause yellow stain (hereinafter referred to as Y-stain) in the nondye-image portion has been a long-felt demand in the art.
As compared with the yellow and cyan couplers magenta couplers are liable to cause more significant Y-stain by light, moisture, or heat in the non-dye-image portion, as well as fading caused by light in the dye-image portion, and this disadvantage often incurs a problem.
The couplers commonly used for forming magenta dye images are 1,2-pyrazolo-5-ones. The magenta dyes formed from the 1,2-pyrazolo-5-one magenta couplers have disadvantages in having secondary spectral absorption in the vicinity of 430 nm, in addition to the primary spectral absorption in the vicinity of 550 nm which leads to poor color reproduction. Therefore, various studies have been conducted to solve this problem.
The magenta coupler having an anilino group on the 3 position of 1,2-pyrazolo-5-one, which exhibits less significant secondary absorption, and known to be useful in obtaining color images for print. The related techniques are disclosed, for example, in U.S. Pat. No. 2,343,703, and British Patent No. 1,059,994.
These magenta couplers are disadvantageous as they are significantly inferior in the image preservability, especially, in the stability of dye images to light, as well as in larger magnitude of Y-stains in the non-dye image portion.
Other means proposed for limiting the above-mentioned secondary absorption of magenta couplers in the vicinity of 430 nm are magenta couplers such as pyrazolobenzimidazole couplers in British Patent No. 1,047,612; indazolone couplers in U.S. Pat. No. 3,770,447; and pyrazolotriazole couplers in U.S. Pat. No. 3,725,067, British Patent Nos. 1,252,418, and 1,334,515. The dyes formed from these couplers are advantageous in terms of color reproduction, as compared with the previously mentioned dyes formed from 1,2-pyrazolo-5-ones having an anilino group on the 3 position, in having the secondary absorption in the vicinity of 430 nm, and in posing relatively small Y-stain due to light, heat, or moisture, in the non-dye image portion.
However, these couplers are found to have a serious drawback, that is, the gradation of resultant images significantly fluctuate depending on the exposure illumination intensity. It is well known fact that even with a constant exposure amount, the sensitivity of the light-sensitive material greatly varies depending on change in illumination intensity. Correspondingly, various countermeasures have been taken, for example, by changing an exposure amount in compliance with expected sensitivity change, and this drawback does not pose a problem that inhibits common use of the light-sensitive material.
If a light-sensitive material poses significantly great gradation fluctuation depending on exposure illumination intensity (hereinafter referred to as illumination dependency of gradation), this drawback poses a fatal defect to the light-sensitive material. The light-sensitive materials have different gradation designed to comply with the nature of their applications. When such materials are exposed in a practical operation, the suitable exposure illumination intensity naturally varies depending on the exposure conditions; more specifically, the brightness on a subject, in the case of the materials for picture-taking; and in the case of print material, the difference in image density resultant from overexposure or underexposure of the film bearing original image. With the light-sensitive material whose gradation having greater illumination dependency, the resultant gradation will deviate from the allowable range of designed gradation.
As a result, some scenes may have excessively hard gradation, thereby details especially in low density and high density areas can be missing, or some scenes may have excessively soft gradation and may be dull. In both cases, the quality of the light-sensitive material is significantly jeopardized.
In the case of print light-sensitive material, various print sizes are available. Commonly used sizes range from the smallest format known as "E size" to the whole sheet size. Usually, a user prints several scenes onto a small-sized photographic paper, and then the user selects preferable scenes and enlarges them to larger size prints. In this course, the film bearing the original image is the same regardless of the size of a print paper, larger or smaller. Additionally, the intensity of the light source cannot be readily intensified. Therefore, it is unavoidable that when an original image is enlarged onto a large-sized print, the exposure illumination intensity relative to the print light-sensitive material is inappropriately low. As a result, with a light-sensitive material whose gradation being significantly dependent on exposure illumination intensity, the larger print will have poor image quality and fail to satisfy the user, even this type of material may provide good image quality with a smaller print.
As described earlier, an improved exposure apparatus can cope with sensitivity change corresponding to exposure illumination intensity, to an extent not adversely affecting practical exposure operations. However, measures including improved apparatuses such as exposure apparatuses have difficulties in coping with gradation change. Therefore, it is necessary to improve illumination dependency of gradation, by means of improved light-sensitive materials.
One method to improve illumination dependency of gradation, the use of iridium compounds, is disclosed in Japanese Patent Publication Open to Public Inspection (hreinafter referred to as Japanese Patent O.P.I. Publication) Nos. 97648/1986, and 954/1987.
However, once such a compound is added in an amount enough to ensure its effect, adverse effects often occur as evidenced by desensitization, and deteriorated pressure-resistance of the light-sensitive material. Therefore, the use of such compounds has limitation.
Additionally, if the previously mentioned pyrazolotriazoles are used in conjunction, fogging readily occurs. And this disadvantage poses problems that hinder practical use of this method.